JP4269283B2 - In-mold coating molding method - Google Patents

Description

  In the present invention, after a resin molded product is molded in a mold, a part of the surface of the resin molded product is covered with a paint (sometimes referred to as coating) without removing the resin molded product from the mold. The present invention relates to a coating molding method.

  As a method for improving the decorativeness of a resin molded product, many decorations by painting have been conventionally used. A conventional coating method is generally a method in which a resin molded product injection-molded in a mold is taken out of the mold, and then a coating is applied to the surface by a spray method, a dipping method, or the like. The applied paint becomes a strong coating film (sometimes referred to as a coating film) by curing and decorates and protects the surface of the resin molded product.

  However, in recent years, for the purpose of omitting the process of the coating method, an in-mold coating molding method (also referred to as an in-mold coating method) in which molding of a thermoplastic resin and coating with a coating film are performed in the same mold Has been proposed).

One example of the in-mold coating forming method will be briefly described below with reference to the flowchart of FIG. In the conventional in-mold coating molding method shown in FIG. 7 (1), a thermoplastic resin is used as a base material, injection molding is performed in the mold, and then the resin is cooled and contracted in the mold to mold in the mold. A gap (sometimes referred to as a gap) is formed between the resin molded product and the mold cavity surface, and a paint is injected into the gap using a paint injection machine.
After injecting the paint, the paint is cured in the mold, and after the paint is dried and cured, the mold is opened and the resin molded product covered with the paint is taken out from the mold.

Another example of the in-mold coating forming method will be briefly described below with reference to the flowchart of FIG. In the conventional in-mold coating forming method shown in FIG. 7 (2), the mold is slightly opened after injection molding in a mold using a thermoplastic resin as a base material.
Then, by slightly opening the mold, paint is applied to the gap (also referred to as a void) formed between the resin molded product molded in the mold and the mold cavity surface using a paint injection machine. inject.
After injecting the paint, the mold is re-clamped to allow the paint to flow uniformly on the surface of the resin molded product, and then the paint is cured. After the paint is cured, the mold is opened and coated with the paint. The resin molded product is taken out from the mold as an in-mold coated molded product.

In the in-mold coating molding method, since the molding of the thermoplastic resin and the coating with the paint are performed in the same mold, it is possible to reduce the cost by omitting the process and at the same time before the floating dust is cured. It is possible to obtain a high-quality product with almost no defects such as adhesion to the coating film.
For this reason, use of the above-described in-mold coating forming method is being studied for many parts such as bumpers, doors, door mirror covers, and fenders that require high quality in appearance.

For these reasons, many proposals have already been made for the above-described in-mold coating forming method, and for example, those disclosed in Patent Documents 1 and 2 are known.

JP 2002-172657 A JP-A-9-52257

Here, the coating material used in the above-mentioned in-mold coating forming method generally has a characteristic that the viscosity before curing is very small and flows into a slight gap.
Therefore, when performing the conventional in-mold coating forming method, there is a problem that the paint before curing leaks out of the mold cavity from the mold parting surface or the like and adheres to the mold.

If the leaked paint is left as it is, it will harden at the leaked part, which may damage the mold in the subsequent molding, and may cause the molded product to be fouled. It becomes. Therefore, when the paint leaks from the mold cavity, it is necessary to temporarily stop the molding and clean the mold, and this cleaning is a great obstacle to continuous molding.

In order to solve this problem, the conventional mold for in-mold coating molding is provided with a seal mechanism or the like at a portion where the paint easily leaks to prevent the paint from leaking.
Examples of the sealing mechanism include, for example, a coating material leakage prevention mechanism (sealing member) as described in Patent Document 2, a parting surface that has a cut-off structure, and a mold curing heater with a coating curing heater. A method of forcibly curing the paint to prevent the paint from leaking is already known.

However, here, in order to adopt the above-described conventional sealing mechanism, it is necessary to greatly modify the mold, and there is a problem that the structure of the mold is complicated and expensive.
In particular, in the case of the prior art in which the sealing mechanism is configured with a parting surface as a cut-off structure, it may not be structurally usable depending on the product shape, and the shape of the resin molded product is limited due to restrictions on mold processing. There were many cases.
In addition, the conventional seal mechanism, which greatly depends on the structure of the mold, may require modification of the mold when the coating thickness is changed by changing the specifications of the in-mold coated product. Many.

In addition, in the in-mold coating molding method, in many cases, the surface of one half of the resin molded product is coated at a time because the coating material is injected into the entire mold cavity surface on which the coating material injection machine is disposed.
However, depending on the appearance required for the in-mold coated molded product, it may be necessary to coat only a part of the resin molded product. For example, a star mold is placed on the surface of the resin molded product on which the paint injection machine is arranged. In some cases, a heart-shaped coating must be applied.
In general, such a coating is referred to as a partial coating. In such a case, it is necessary to arrange a sealing mechanism in the mold in advance assuming the shape of the partial coating.
Therefore, when a situation occurs in which the shape of the partial covering needs to be changed, it is necessary to greatly modify the mold, and it is very difficult to deal with the change related to the shape of the covering part. .

The present invention has been made in view of the above problems, and solves the problem of the prior art that the paint before curing leaks out of the mold cavity and damages the mold, so that continuous molding is stably performed. The present invention provides an in-mold coating molding method that can flexibly cope with partial coating.

In order to solve the above-described problems, an in-mold coating molding method according to the present invention includes (1) a surface of a resin molded product having a mold cavity formed by a fixed mold and a movable mold and molded by the mold cavity. A mold for forming a resin molding is formed by filling a mold cavity formed by clamping the mold with a resin, using a mold for in-mold coating molding provided with a coating material injection machine for coating the substrate. 1 step, the second step of opening the mold after cooling until the shape can be maintained even if the resin molded product molded in the mold cavity is opened, the resin when the mold is opened a mold cavity surface spaced moldings and mold opening direction, the peripheral portion that covers, and a third step of placing the sheet in a portion not coated, re-type the mold in a state of arranging the sheet Resin molded product molded in the mold cavity by fastening and the mold cavity A fourth step of generating a gap with the surface, and a fifth step of injecting a coating material into the gap to cover the resin molded product, and sequentially from the first step to the fifth step It was configured to do.

(2) In the in-mold coating forming method according to (1), the sheet is formed in a frame shape surrounding an outer peripheral portion of a mold cavity.

(3) In the in-mold coating forming method according to any one of (1) and (2), the sheet is formed of a material to which a paint is more likely to adhere than the metal forming the mold cavity; did.

The in-mold coating molding method according to the present invention provides a sheet between the resin molded product molded in the mold cavity and the mold cavity surface at the boundary between the part coated with the paint and the part not coated. As a result, a gap for injecting the paint is formed, and a seal mechanism for preventing the paint from leaking from the covered portion to the uncovered portion is formed. Therefore, according to the present invention, the thickness of the coating can be adjusted by changing the thickness of the sheet, and the reproducibility of the thickness is high.
And the method of this invention which adjusts the space | gap for paint injection | pouring by the thickness of a sheet | seat does not need to use the metal mold | die of what is called a cutting-off structure, and can simplify the structure of a metal mold | die.
In addition, by forming and arranging the sheet in a frame shape so as to surround the portion to be coated with the resin molded product, it is possible to more reliably prevent the paint from leaking and ensure the coating film thickness.

  Further, in the case of partially covering a resin molded product by the in-mold coating molding method, if the present invention is applied, it can be easily handled by changing the shape of the sheet, and the shape in which the coating range is desired. Can be changed.

  Furthermore, if the material of the sheet is selected as a material to which the paint adheres more easily than the metal that forms the mold cavity surface, the sheet is cured at the portion where the paint leaks, and the mold is damaged by the subsequent molding. The problem can be prevented, the mold can be easily cleaned after molding, and the excellent effect that continuous molding can be performed stably can be obtained.

Hereinafter, preferred examples of the in-mold coating forming method according to the present invention will be described with reference to the drawings.
1 to 6 relate to an embodiment of the present invention, and FIGS. 1 and 2 are diagrams for explaining a schematic structure of an in-mold coating mold used in the present embodiment. FIG. 2 (1) is a plan view of the movable mold viewed from the fixed mold side and a sectional view of the substantial section thereof, and FIG. 2 (2) is a fixed mold viewed from the movable mold side. It is the top view of a type | mold, and its principal part sectional drawing.
FIG. 3 is a view for explaining the arrangement of sheets used in the present embodiment.
FIG. 4 is a conceptual diagram showing the behavior of a resin, a sheet, and a paint for explaining the steps of the in-mold coating molding method, and FIG. 5 is a flowchart describing the steps of the in-mold coating molding method.
FIG. 6 is a diagram for explaining the shape of the sheet used in the present embodiment.

A preferred example of the in-mold coating mold 100 (also referred to as the mold 100) used in the present embodiment will be described in detail below with reference to FIGS.
A mold 100 shown in FIG. 1 includes a movable mold 10, a fixed mold 20, a paint injector 50, and the like. A mold cavity 15 A formed in the movable mold 10 and a mold cavity formed in the fixed mold 20. The mold cavities 15 having a desired shape are formed in the mold 100 by combining and clamping the 15Bs so as to face each other.
Here, the mold 100 shown in FIG. 2 is a center gate mold in which the gate portion 8 is formed in the vicinity of the center of the mold cavity 15 </ b> B, and the shape of the resin molded product molded in the mold cavity 15. Is a shape in which a side wall is formed around a rectangular flat plate so as to surround the outer periphery thereof.

In the present invention, in order to sandwich the sheet S between the resin molded product and the mold cavity surface, the mold cavity surface, the resin molded product, It is necessary to once separate the portion where the paint is likely to leak between the two, and in the separated state, it is necessary to have the shape of the mold cavity 15 in which the sheet S can be disposed.

Here, the portion where the paint is liable to leak is generally at the boundary between the portion covered with the resin molded product and the portion not covered. For example, the portion of the mold cavity on the side where the paint injection machine is disposed is coated with the paint. In the case where the surface of one half of the resin molded product is coated by injecting the resin, the vicinity of the mold dividing surface is the boundary portion.
In such a case, if the coating material leaks from the coating portion to the non-covering portion, the coating material flows into the mold dividing surface and cures there, causing the above-described problem of mold damage.
In addition, when the above-described partial coating is performed, if the paint flows out to a portion that is not covered, there is a problem that the boundary of the covered portion is not clear.

Here, the shape of the mold cavity 15 of the mold 100 described in FIG. 1 is such that a side wall is formed so as to surround the outer periphery of the flat plate, and the entire mold cavity surface on the side where the coating material injection machine is disposed. The mold structure is such that the paint is poured into the surface to cover the surface of one half of the resin molded product.
Therefore, since the boundary portion between the portion to be coated and the portion not to be coated of the in-mold coated molded product of the mold 100 is a side wall portion formed on the mold dividing surface, the mold cavity 15B formed to form the side wall. The shape of the groove portion is formed to be slightly larger on the outer peripheral side in a direction substantially perpendicular to the mold opening / closing direction, and thereby a resin portion (also referred to as a seal portion) for sandwiching the sheet S between the mold cavity surface Form).
Although details will be described later, in the embodiment shown in FIG. 1, the molded seal portion for sandwiching the sheet S between the mold cavity surface is cut off and removed after molding the in-mold coated molded product (trimming process). )
Of course, depending on the shape of the desired in-mold coated molded product, the sealing portion by the sheet may be provided on the extension of the surface portion to be coated without lowering by one step.

Next, the configuration of the paint injector 50 will be briefly described.
The paint injection machine 50 according to the present embodiment is attached to the movable mold 10 and can inject the paint into the mold cavity 15 from the paint injection port 51 provided on the mold cavity surface of the movable mold 10. It is configured as follows.
In addition, a valve (not shown) is attached to the coating material injection port 51 of the coating material injection machine 50. When the resin J as the base material is injection-molded, the valve is closed so that the mold 100 of the mold 100 is closed. The resin J injected into the mold cavity 15 is prevented from entering the paint injector 50 from the paint injection port 51.

And the coating material injection machine 50 in this Embodiment is driven by the drive device which is not shown in figure, and can inject | pour into the metal mold | die cavity 15 exactly the desired quantity of the coating materials T for coat | covering a resin molded product. It is configured as follows.
In addition, although the coating material injection machine 50 in this Embodiment was comprised so that the coating material T might be inject | poured from the mold cavity surface by the side of the movable mold | type 10, it is not restricted to this, The resin molding shape | molded in the mold cavity 15 What is necessary is just to comprise so that a coating material can be inject | poured into the space | gap part produced between the part to coat | cover the product and the mold cavity surface, and the coating material injection | pouring machine 50 may be attached to the fixed mold | type 20 if the conditions are satisfy | filled. .

Next, the arrangement and configuration of the sheet S used in the present embodiment will be described.
As described above, the characteristic point of the present invention is that the sheet S sandwiched between the resin molded product and the mold cavity surface is sealed with the paint T leaking from the mold cavity 15 and the sheet S The thickness of the coating film is adjusted by the thickness.
As described above, in order to sandwich the sheet S between the resin molded product and the mold cavity surface, in the mold opening process after the molding of the resin molded product, at the portion where the sheet S is sandwiched, It is necessary to separate from the resin molded product.

Here, since the resin molded product molded by the mold 100 shown in FIG. 1 remains in the fixed mold 20 after the mold is opened, the mold cavity surface formed on the movable mold 10 and the resin molded product are separated from each other. The paint T injected from the paint injection machine 50 flows on the flat plate and reaches the side wall portion.
Note that, as described above, in the mold 100, the portion covered by the in-mold coated molded product is the surface on the movable mold 10 side. Therefore, in the mold 100, it is necessary to arrange the sheet S adjacent to the side wall portion formed along the outer peripheral portion of the flat plate so that the paint T does not flow into the mold parting surface from the covered portion. Thus, this has a shape corresponding to the shape of the seal portion of the resin molded product described above.

Further, the material of the sheet S will be described. The sheet S may be made of a material that does not damage the mold cavity 15 when sandwiched between the mold cavity surface and the resin molded product, and the thickness thereof is resin molded. It is preferable to select in consideration of the thickness of the coating film to be coated on the product.
Therefore, the sheet S is preferably a film-like resin sheet having a smooth surface, and is preferably not damaged by pressure or heat at the time of coating the paint. In addition, a foam sheet can be used as the sheet S so that the sheet S can be handled easily.
In view of the thickness of the coating film to be coated by a general in-mold coating method, the thickness of the sheet S is suitably in the range of about 10 μm (micrometer) to 2 mm.

In addition, a small amount of paint T may enter between the mold cavity surface and the sheet S during the in-mold coating, but the paint T is more likely to adhere to the sheet S than the mold cavity surface. If it is formed, the paint T is naturally removed from the mold cavity surface when the in-mold coated molded product is taken out from the mold 100, so that it is not necessary to remove it by labor. Is preferably a material having a large adhesiveness to the paint T.

If the sheet S is made of resin, it can be easily cut (trimming) by a cutter knife or the like, and the cutting operation can be industrially automated.

  In addition, in the metal mold | die 100 shown in FIG. 1, it was set as the structure removed with the sealing part of the resin molded product by trimming, with the sheet | seat S adhering to the resin molded product after solidification. However, the sheet S normally does not adhere to the solidified resin molded product and easily peels off, so that only the sheet S can be removed from the resin molded product without trimming. Depending on the shape of the resin molded product to be molded, the sheet S is sandwiched between the mold cavity surface and the resin molded product without having to bother forming an extra portion such as a seal portion on the resin molded product. In such a case, of course, if only the sheet S is removed from the resin molded product, there is no need for trimming.

  The sheet S may basically have a single layer structure or a multilayer structure. In the case of the multilayer structure, the material of the layer forming the surface in contact with the resin J and the paint T is attached. It is only necessary to satisfy the conditions as the material of the sheet S in terms of property and peelability.

なお、ＡＢＳはアクリルニトリル−ブタジエン−スチレン三元共重合体樹脂の略称、ＰＣはポリカーボネイトの略称、ＰＰはポリプロピレン樹脂の略称、ＰＥはポリエチレン樹脂の略称、ＰＥＴはポリエチレンテレフタレートの略称、ＰＡはナイロン等を含むポリアミド系樹脂の略称である。また、プラグラスは、大日本塗料株式会社製の型内被覆成形用塗料である。

ABS is an abbreviation for acrylonitrile-butadiene-styrene terpolymer resin, PC is an abbreviation for polycarbonate, PP is an abbreviation for polypropylene resin, PE is an abbreviation for polyethylene resin, PET is an abbreviation for polyethylene terephthalate, PA is an abbreviation for nylon, etc. Is an abbreviation for polyamide-based resin. The pluglass is a paint for in-mold coating molding manufactured by Dainippon Paint Co., Ltd.

  Hereinafter, a preferred example of the in-mold coating forming method according to the present invention will be described with reference to FIGS. The embodiment described below utilizes a so-called normal injection molding method in which the mold is not opened at the time of resin injection and filling. However, the molding method at the time of injection and filling of resin J that can be applied to the present invention is applied to this. The method is not limited, and may be an injection press molding method or an injection compression molding method, and is not particularly limited.

In the in-mold coating forming method shown in FIG. 4, as a first step, the movable mold 10 and the fixed mold 20 are clamped by a mold clamping device (not shown), thereby moving the movable mold 10 and the fixed mold 20. After the mold cavity 15 is formed, the thermoplastic resin J as a base material is injected into the mold as shown in FIG. 4B (in this embodiment, ABS resin: UMGABS as the base material). UT20B manufactured by the company).

  Next, as a second step, after cooling the resin molded product molded in the mold cavity 15 to such an extent that the shape can be maintained even when the mold is opened, as shown in FIG. Is moved to the anti-fixing mold 20 and the mold 100 is largely opened.

Then, after the movable mold 10 and the fixed mold 20 are greatly separated and the mold 100 is completely opened, the process proceeds to the third step, and as shown in FIG. In the meantime, the sheet S is disposed at a predetermined position by a sheet feeder (not shown).
The material of the sheet S used in this embodiment is a single layer PET (polyethylene terephthalate) resin, and the thickness of the sheet S is about 0.15 mm.

Next, as a fourth step, as shown in FIG. 4 (5), the mold 100 is again clamped by a mold clamping device (not shown), and the gap between the mold cavity surface and the seal portion of the resin molded product is measured. The mold 100 is clamped with the sheet S sandwiched therebetween.
At this time, due to the thickness of the sandwiched sheet S, a slight gap is generated between the mold cavity surface and the resin molded product.

After the gap is generated, the process proceeds to the fifth step, and the paint T is injected into the gap by the paint injector 50 as shown in FIG. In the present embodiment, after generating the gap, 3 ml (milliliter) of the paint T was injected into the gap from the paint injection port 51 by the paint injection machine 50. In addition, the coating surface area of the molded product shape | molded with the metal mold | die 100 used in 1st Embodiment is 300 cm < ² >, and the thickness of the coating film by the coating material T will be about 0.1 mm. As the paint T, pluglass # 8000: red (manufactured by Dainippon Paint Co., Ltd.) was used.
In addition, when the paint does not spread over the entire coated portion only by the injection of the paint, the mold clamping force may be increased after the injection of the paint.

Here, the thickness of the coating film by the paint T is affected by the sheet thickness when the sheet S is sandwiched and clamped, the amount of deformation of the mold cavity 15 caused by the clamping force when the paint is injected, and the like. Therefore, for example, when a polyethylene cross-linked foam having a thickness of about 1 mm is used as the sheet S, the mold cavity due to the sheet thickness (about 0.2 to 0.3 mm) and the clamping force when the mold is clamped Depending on the amount of deformation (slight amount), the thickness of the coated film actually becomes approximately 0.15 mm.
The thickness of the sheet S when the mold is clamped and the amount of deformation of the mold cavity 15 when the paint is injected are determined by the type of the sheet S to be used and the molding conditions when the paint is injected. In consideration of the above, it is possible to obtain a coating film having a desired thickness by using the sheet S having a slightly larger thickness than the desired coating film thickness.

After the coating material is injected, the coating material is hardened in the mold cavity 15, and then the process proceeds to a sixth step. The resin molded product covered by opening the mold 100 is taken out from the mold 100 as an in-mold coated product.
Thereafter, as shown in FIG. 4 (8), the excess seal portion is trimmed and deleted from the in-mold coated molded product.

In the present embodiment, the shape of the sheet S as shown in FIG. 6 (1) is used. However, the present invention is not limited to this, and for example, as shown in FIG. 6 (2). It may have a shape as shown, and any shape that allows the sheet S to be arranged at the boundary between the portion to be covered and the portion not to be covered may be used.
Further, if the sheet S is used as a seal-type sheet so that the sheet S can be affixed to a desired portion in the third step described above, the molding becomes efficient.

It is principal part sectional drawing explaining the structure of the metal mold | die for in-mold coating shaping | molding used for embodiment of this invention. It is principal part sectional drawing explaining the structure of the fixed mold | type and movable mold | type of the metal mold | die for in-mold coating | molding used for embodiment of this invention. It is a conceptual diagram for demonstrating arrangement | positioning of the sheet | seat used for embodiment of this invention. It is the conceptual diagram which showed the behavior of resin, a sheet | seat, and a coating material in each process of the in-mold coating molding method concerning embodiment of this invention. It is the flowchart which described the process of the in-mold coating method concerning embodiment of this invention. It is a figure for demonstrating the shape of the sheet | seat used for this embodiment. It is a flowchart explaining the process of the in-mold coating method by a conventional method.

Explanation of symbols

8 Gate 15 Mold cavity 15A Mold cavity (movable mold side)
15B Mold cavity (fixed mold side)
DESCRIPTION OF SYMBOLS 10 Movable type | mold 20 Fixed type | mold 50 Paint injection machine 51 Paint injection port 100 Mold | mold for in-mold coating J Resin S Sheet T Paint

Claims (3)

A mold for in-mold coating molding having a mold cavity formed by a fixed mold and a movable mold, and having a coating material injection machine for coating the surface of a resin molded product molded by the mold cavity A first step of filling a mold cavity formed by clamping the mold with a resin to form a resin molded product, even if the resin molded product molded in the mold cavity is opened The second step of opening the mold after cooling until the shape can be maintained , the periphery of the portion to be coated with the mold cavity surface that is spaced apart from the resin molded product in the mold opening direction when the mold is opened in, and a third step, a resin molded article molded by the mold cavity by re clamping the mold in a state of arranging the sheet and the mold cavity surface placing the sheet in a portion not coated A fourth step of creating a gap between the first and second, and injecting paint into the gap Fifth comprising a step, mold coating molding method of the resin sequentially performed from the first step to a fifth step of coating a resin molded article Te.   The in-mold coating forming method according to claim 1, wherein the sheet is formed in a frame shape surrounding an outer peripheral portion of a mold cavity.   The in-mold coating forming method according to claim 1 or 2, wherein the sheet is formed of a material to which a paint is more easily attached than a metal forming a mold cavity.

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